My understadning is that illicit sacraments can be efficacious for one in material schism, though never for someone in a state of formal schism.
That having been said, I don’t see what this has to do with Gene’s question.
As far as marriage is concerned, the Orthodox are no different from Protestants. This is because, in and of itself, the sacrament does not require a priest to affect its validity. The ministers of Matrimony are not the ordained priest, but the bride and groom.
The Church however, with the authority given her by Christ, has added other requirements to making a marriage valid. One of these is that, for a mixed marriage, approval must be given by the Catholic Ordinary. Without this, the marriage is both illict and invalid. Here’s what the Code of Canon Law says on the subject:
This last part I find really confusing. I don’t know why it means; nor do I see why there should be an exception for the schismatic Eastern Chuches, since marriage, in itself, has nothing to do with the sacred orders of a priest.
Maybe one of the staff apologists can help us out.